ACI Concrete Strength Testing Technician Practice Test

What does the ASTM C39 test measure in regards to concrete specimens?

1. Flexural strength

2. Shear strength

3. Compressive strength

4. Tensile strength

The correct answer is: Compressive strength

The ASTM C39 test is specifically designed to measure the compressive strength of concrete specimens. This is a critical property of concrete, as it indicates the material's ability to withstand axial loads without failing. During the test, cylindrical concrete samples are subjected to a controlled loading process until they fail, and the maximum load applied at failure is used to calculate the compressive strength. Compressive strength is a vital parameter in structural engineering, as it directly affects the performance and safety of concrete structures under various load conditions. The test provides valuable data that helps engineers and architects to ensure that the concrete used in construction meets the required strength specifications for design purposes. The other options—flexural strength, shear strength, and tensile strength—are different properties measured by different tests. Flexural strength pertains to the material’s ability to resist deformation under load, shear strength is concerned with the material's ability to withstand sliding failures along a plane, and tensile strength measures resistance to being pulled apart. Each of these properties is important but is assessed using distinct testing methods apart from ASTM C39.